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Is daylight saving time bad for your health?

A group of scientists published a commentary on previously studied effects of daylight saving time to answer the question, ‘is daylight saving time bad for your health?’

A group of scientists from Vanderbilt University Medical Center recently published a commentary in JAMA Neurology, on the topic of daylight saving time and whether this practice of moving clocks forward and backward is damaging to our health.

The widespread popularity of daylight saving time began around the time of the First World War in order to mimic practices that were being used in some European countries at the time. The official practice of daylight saving time was instituted in the United States during the ‘Uniform Time Act of 1966’, soon after which Canada followed suit in order to maintain unity for economic and social purposes. The main purpose for which daylight savings was proposed, was for energy conservation and certain safety measures. But early on, the US Department of Transportation, who were responsible for the enforcement and evaluation of daylight saving time, reported that “the potential benefits to energy conservation, traffic safety, and reductions in violent crime were minimal”. In addition, in 2008 the US Department of Energy investigated the potential impact of an extended period of daylight saving time to national energy consumption and found that total energy consumption was only reduced by 0.02%.

In addition to minimal energy conservation effects, daylight saving time has been associated with negative health outcomes related to blood flow in the brain and circulatory system functioning. For instance, studies have shown that rates of ischemic stroke were higher immediately following daylight saving time. It is believed that the increased risk of negative health outcomes could be linked to the sleep deprivation that occurs when clocks move forward. It has been reported that when clocks are set forward in the spring, people tend to lose around 15-20 minutes of sleep on average. In one study that included high school students, this number went up to 30 minutes less sleep than usual. These are concerning results as multiple sources of research have reported that there are “adverse effects of chronic sleep loss on attention, behaviour, learning problems, depression, and self-harm”.

Recently in Canada, the province of British Columbia has proposed new legislation that would eliminate the practice of setting clocks forward and back each year. Instead, the Premier wants to keep the province permanently on daylight saving time  – one hour ahead of standard time, based on residential support for the idea. A professor from York University believes that the province has the right idea with trying to eliminate daylight saving time, but that it would be more beneficial to individual health if standard time was followed year-round. This is because standard time is more closely aligned with our body’s internal clock.

The main impact daylight saving time has on health is the effect it has on the body’s internal clock, specifically circadian rhythms. Circadian rhythms are “physical, mental, and behavioural changes that follow a daily cycle”. These rhythms have an influence over a variety of regular body functions, and one of the main external cues they respond to is light. Scientists at Vanderbilt University Medical Center believe that the adverse consequences on health associated with daylight saving time could be in relation to the genetic aspects of the body’s circadian rhythms.

More research is required to understand the true cause of the negative consequences associated with daylight saving time, but regardless, these scientists along with many others believe that daylight saving time is indeed bad for health. However, moving away from the practice, and adhering to standard time year-round requires political support.


Written by Haritha Thevar, BSc



Circadian Rhythms. (2019). Retrieved 9 November 2019, from

Coyne, T. (2019). ‘Blame the United States’: B.C. to stick with seasonal time changes until 2020. Retrieved 9 November 2019, from

Daylight Saving Time has long-term effects on health. (2019). Retrieved 9 November 2019, from

Malow, B., Veatch, O., & Bagai, K. (2019). Are Daylight Saving Time Changes Bad for the Brain?. JAMA Neurology. doi: 10.1001/jamaneurol.2019.3780

The History of Daylight Saving Time. (2019). Retrieved 9 November 2019, from

Toronto researchers push to eliminate Daylight Saving Time, switch permanently to Standard Time. (2019). Retrieved 9 November 2019, from


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